Performance of Blue Traces by Kati Gleiser at the Indiana University Jacobs School of Music, October 10, 2013.
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Kati Gleiser, the pianist for whom I wrote Blue Traces, told me about swimming in the ocean at night and marveling at the colorful glow cast from bioluminescent plankton. Moving your arm through the water disturbs the plankton, and in response they set off a bluish trail of soft light. This image gave me the idea for the piece: the piano plays, and the computer creates gently glowing traces of sound. Near the end, everyone becomes more agitated, as if the swimmer were now splashing around and the plankton reacting with more excitement.

All the computer sound comes from live sampling of the piano performance, transformed by various kinds of granulation — a technique that can take a short sound and extend it into a long sustained note.

The piece exists in two forms, as a duo for piano and computer, and the same duo supplemented by a string orchestra.